zmVault/hvac-calculations.md

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		destiny/uncertain status/incomplete topic/construction/electrical type/encyclopedia authorship/original	HVAC Calculations	true

HVAC Calculations

Units

British Thermal Unit

Unit of heat energy

There are several definitions of the Btu, HVAC uses the IT definition, abbreviated Btu_IT

\begin{align*}
1 \text{Btu}_\text{IT} &\equiv \left( 4.1868 \times 453.59237 \times{\frac{5}{9}} \right)~\text{J} \\
&\approx 1055.056~\text{J}
\end{align*}

More common than Btu itself is thousand British thermal units per hour (MBH), a unit of power.

\begin{align*}
1 \text{MBH} &\equiv 1000~\text{Btu/hr} \\
&\approx 3.412~\text{W}
\end{align*}

Ton of Refrigeration (TR or TOR)

Unit of power

[!info] Also Known As

• refrigeration ton (RT)
• ton (refrigeration)

\begin{align*}
1 \text{TR} &\equiv 12000~\text{Btu}_\text{IT}/\text{h} \\
&\approx 3516.853~\text{W}
\end{align*}

Cubic Feet per Minute (CFM)

Unit of volumetric flow

Measures

Airflow

External static pressure (ESP) measured in inches of water

Heating/Cooling Capacity

• Tons (refrigeration)

• MBH

• Entering air temperature (EAT)

• Leaving air temperature (LAT)

• Mixed air temperature (MAT)

• Latent heat

• Sensible heat

• Sensible -> dry bulb

• Latent -> wet bulb

???

• OSA EAT (F)

• EXH EAT (F)

• IN S.L.

• OUT ALT.

Efficiency

• η (eta)